The present invention relates to a spade bit.
Spade bits are generally flat, inexpensive bits having a thickness of generally between 17/200″ and 19/200″, which are commonly used in the construction trade for making clearance holes for electrical and plumbing purposes. Spade bits are also commonly used for drilling bolt holes in deck timbers (4×4 and 6×6).
Spade bits, however, have a number of shortcomings. For instance, spade bits require more axial pressure than a twist drill. Also, as the spade bit begins to get dull, the user must apply more pressure to get the bit to cut chips. The axial force requirement also increases as the depth of the hole increases. Further, the flat spade bit has a tendency to vibrate and shake as it works. The high axial force requirement causes much of the vibration to be transmitted to the user. Another shortcoming of the spade bit is that since considerable axial force is applied, there is a potential for mishap when the hole is completed. The operator must brace himself to maintain balance when the hole is completed. It is not uncommon for the user to bust his/her knuckles against the workpiece.
Other tools could be used to overcome the shortcomings of the spade bit, such as wood boring tools like auger bits, but these tools generally sell for five to ten times the amount that a spade bit will sell. Spade bits are different than wood boring tools because the manufacturing of spade bits does not involve any lathe or turning operations. Wood boring tools typically have helical threads or circular grooves thereon for providing improved pull through of the wood boring tool. Such helical threads or circular grooves, however, have not been able to be provided on spade bits for two reasons: (1) the addition of helical threads or circular grooves to a spade bit would represent an unacceptable cost addition to spade bits; and (2) the typical spade bit is generally only 17/200″ to 19/200″ thick and, therefore, does not offer the same surface area for threads or grooves as a wood boring bit, which typically have a thickness of ¼″ to 3/10″.
Thus, there is a need for a spade bit which overcomes the foregoing shortcomings. The present invention provides such a spade bit. Other features and advantages of the invention will become apparent in view of the specification and the drawings.